Abbreviations
3GPP 3rd generation partnership project
ADC Application detection and control
AF Application Function
BBERF Bearer Binding and Event Reporting Function
CC Charging control
CN Core Network
GW Gateway
ID Identity, Identifier
IMSI International mobile subscriber identity
IP Internet protocol
IP-CAN IP connectivity access network
OCS Online charging system
OFCS Offline charging system
PCC Policy and charging control
PCEF Policy and charging enforcement function
PCRF Policy and charging rules function
P-GW Packet data network gateway
QoS Quality of service
Rel Release
SA Service Architecture (group)
SDF Service data flow
SPR Subscription profile repository
TDF Traffic detection function
TR Technical report
TS Technical Specification
UDR User data repository
UE User equipment
3GPP SA2 has recently approved a work item “Study on Application Based Charging”, refer to 3GPP S2-122533. 3GPP has also other traffic detection and charging related work going on within the area of fixed broadband interworking, refer e.g. to the 3GPP SA2#91 meeting report. The study concentrates on “PCEF and/or TDF based charging solutions” with a requirement of “Charging for services and applications when TDF performs application detection and control for IP-CAN session's traffic”. In practice an essential issue and objective for many companies is to specify how a standalone TDF can perform/support application based charging.
According to 3GPP TS 23.203 v 11.5.0, the TDF is a functional entity that performs application detection and reporting of detected application and its service data flow description to the PCRF.
For those cases where service data flow description is not possible to be provided by the TDF to the PCRF, the TDF performs:                Gating;        Redirection;        Bandwidth limitation.for the detected applications.        
For those cases where service data flow description is provided by the TDF to the PCRF the actions resulting of application detection may be performed by the PCEF as part of the charging and policy enforcement per service data flow and by the BBERF for bearer binding as defined in 3GPP TS 23.203 v 11.5.0 or may be performed by the TDF.
For the purposes of this specification, it is sufficient that the TDF performs at least detection of a start of an application.
FIG. 1 shows how the TDF conventionally may be embedded in the PCC logical architecture. In detail, the TDF is connected via the Sd interface to the PDRF. The PCRF has a central role in the PCC architecture and is connected to the PCEF via Gx interface. Typically, the PCEF is embedded in a gateway function. Furthermore, the PCRF and the PCEF may be connected to an OCS. The PCEF may be additionally connected to an OFCS.
Further details are provided in 3GPP TS 29.212.